1. Technical Field
The invention concerns ground plane systems used in RF applications and more particularly, ground planes that can be dynamically added and removed from an RF system.
2. Description of the Related Art
Ground planes are widely used in RF systems for a variety of applications. For example, ground planes are often used in microwave antenna systems as reflectors and shielding elements. When used as reflector elements, ground planes are commonly spaced a multiple of one quarter wavelength from a radiating element. Common configurations include a plurality of antenna elements arranged on one side of a dielectric sheet to form an array with the ground plane spaced on an opposing side of the dielectric sheet or spaced below the sheet. In either case, such arrangements provide satisfactory results and have been widely used where the radiating elements are only required to operate over a narrow band of frequencies.
Even in those instances where two or more sets of radiating elements are disposed on a common surface of one dielectric sheet, a single ground plane can be used if the radiating elements operate on a harmonically related set of frequencies, provided that the spacing between the radiating elements and the ground plane is maintained at some multiple of a quarter wavelength at the operating frequency.
A more difficult problem arises when the antenna radiators are designed to operate over multiple bands of RF frequencies that are not harmonically related. One technique uses a stepped ground plane arrangement in which groups of radiating element for each frequency are positioned in selected areas of the dielectric substrate. The ground plane in the area beneath each group of radiating elements is stepped up or down to provide the proper spacing needed for operation for each group of antenna elements. However, the use of this stepped approach can present engineering tradeoffs that negatively affect the operation of each antenna array.